That thought has occurred to me as well. Putin can get one of the 12 GRU officers to "volunteer" to act as a defendant. Offer him up for extradition. Fly him to New York and go to immigration and say "Here I am, arrest me."
Then get the lawyers involved in discovery. Demand that the servers be seized and held under the authority of the Court, and that they be made available to the defense for an "independent" forensic examination. And demand a speedy trial.
In all likelihood, Putin will not do this. He will thumb his nose at these indictments. And that's probably what he should do.